Portal de Pesquisa da BVS Veterinária

Tese em Português | VETTESES | ID: vtt-218122

Resumo

A aquicultura atualmente é um dos principais meios de obtenção de alimentos de origem aquática no mundo e sua produção global corresponde a 47% da produção mundial de organismos aquáticos, o equivale a mais de 80 milhões de toneladas. Dos grupos produzidos, destaca-se a produção de crustáceos que, em 2016, foi de 7,9 milhões de toneladas, com o Litopenaeus vannamei, sendo responsável por 65,3% deste total. Porém, essa produção vem sendo constantemente ameaçada por surtos de doenças, fazendo-se necessária uma abordagem produtiva que aplique medidas de biosseguridade, nutrição adequada, promoção da imunidade dos animais cultivados e manutenção da boa qualidade de água, para mantimento da homeostase, o que traduz-se no sistema de bioflocos (BFT). Entretanto, embora L. vannamei mantidos nesse sistema alcançem melhores índices zootécnicos quando comparados a sistemas tradicionais, pouco se sabe sobre a influência da transferência de animais para os diferentes sistemas de cultivo, durante a fase de berçário, no desempenho zootécnico e resistência imunológica ao Vírus da Síndrome da Mancha Branca-WSSV. Portanto, o objetivo do presente estudo foi avaliar a influência da exposição e alteração do sistema de cultivo sob o desempenho zootécnico e resistência imunológica ao WSSV de Litopenaeus vannamei, durante a fase de berçário. Foram avaliados dois sistemas, Bioflocos BFT e Recirculação de Água Clara RAC, em três etapas: a primeira etapa, onde as pós-larvas de 10 dias (Pl10s - 290PL/g), foram mantidas por um período de 10 dias nos respectivos sistemas; segunda etapa, com duração de 30 dias, que consistiu na redistribuição das Pl20s para ambos os sistemas, obtendo-se assim quatro tratamentos (BFT-BFT, BFT-RAC, RAC-BFT e RAC-RAC) e; a terceira etapa, correspondente ao desafio viral. Foram avaliadas variáveis de desempenho zootécnico; contagens total e diferencial de hemócitos; determinação de taxa de infecção e lesões sugestivas de WSSV via nested-PCR e histologia, respectivamente e; contagem presuntiva de Vibrio sp. O sistema BFT quanto ao desempenho zootécnico, de um modo geral, mostrou-se eficiente, especialmente nas primeiras fazes de vida do animal. com melhores resultados quando comparado ao RAC. Os resultados da contagem presuntiva de Vibrio sp. demonstraram crescimento nos tratamentos oriundos ou mantidos em BFT. No que se refere à resposta imunológica e a influência dos sistemas, os parâmetros hemato-imunológicos não foram influenciados, porém observou-se que em um cenário de infecção por WSSV, houve interferência na resposta imune do animal, resultando na diminuição da quantidade de células imunocompetentes. Além disso, entre os tratamentos, houve diferença na forma de manifestação da doença, como constatado através da análise histológica devido a maior concentração de lesões sugestivas registradas em animais oriundos ou mantidos em BFT. Entretanto, apesar das diferenças nas lesões encontradas, todos os animais desafiados foram positivos para WSSV via nested-PCR. Diante disso, concluiu-se que apesar do BFT ser considerado um ambiente biosseguro para os animais cultivados, por ser um sistema de troca mínima ou nula de água, em um cenário de infecção por WSSV, pode induzir a um estado de fadiga dos sistema de defesa dos animais cultivados decorrente da estimulação contínua do sistema imunológico devido aos microrganismos constantes nos flocos, podendo levar os animais a uma condição de maior vulnerabilidade. E embora não tenha sido avaliado um cenário de co-infecção por WSSV e Vibrio sp., a possibilidade de sua ocorrência resultaria na potencialização da infecção por WSSV, especialmente no sistema com BFT, considerando as altas concentrações vibrionaceas contabilizadas.

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Aquaculture is currently one of the main means of obtaining food of aquatic origin in the world and its global production corresponds to 47% of the world production of aquatic organisms, equivalent to more than 80 million tons. Of the groups produced, the production of crustaceans stood out, which in 2016 was 7.9 million tons, with the marine shrimp, Litopenaeus vannamei, accounting for 65.3% of this total. However, this production has been constantly threatened by disease outbreaks, requiring a productive approach that applies biosecurity measures, adequate nutrition, promoting the immunity of cultivated animals and maintaining good water quality, to maintain homeostasis, which translates into if in the biofloc system (BFT). However, although L. vannamei kept in this system has achieved better zootechnical rates when compared to traditional systems, little is known about the influence of the transfer of animals to different cultivation systems, during the nursery phase, on zootechnical performance and immune resistance to White Spot Syndrome Virus WSSV. Therefore, the objective of the present study was to evaluate the influence of Litopenaeus vannamei exposure, during the nursery phase, and the alteration of the culture system, on zootechnical performance and immunological resistance to WSSV. Two systems were evaluated, Biofloc - BFT and Clear Water Recirculation - CW, in three steps: the first step, where the 10-day post-larvae (PL10s - 290PL/g), were maintained for a period of 10 days in the respective systems; second step, lasting 30 days, which consisted, at the end of the 1st stage, in the redistribution of the Pl20s for both systems, thus obtaining four treatments (BFT-BFT, BFT-CW, CW-BFT, and CW-CW) and the third step corresponding to the viral challenge. In these steps, it was determined: zootechnical performance variables; hematological variables (total and differential hemocyte counts); presumptive total count of Vibrio sp.; lesions suggestive of WSSV infection via histology and; infection and survival rate after viral challenge. The BFT system in terms of zootechnical performance, in general, proved to be efficient, especially in the early stages of the animal's life, with better results when compared to RAC. The results of the presumptive count of Vibrio sp. demonstrated growth in treatments originating from or maintained in BFT. Concerning the immune response and the influence of systems, hemato-immunological parameters were not influenced, however, it was observed that in a scenario of infection by WSSV, there was interference in the animal's immune response, resulting in a decrease in the amount of immunocompetent cells. Also, between treatments, there was a difference in the form of manifestation of the disease, as evidenced by histological analysis due to the higher concentration of suggestive lesions recorded in animals originating or maintained in BFT. However, despite the differences in the lesions found, all challenged animals were positive for WSSV via nested-PCR. Therefore, it was concluded that although BFT is considered a biosafety environment for cultivated animals, as it is a minimal or no water exchange system, in a WSSV infection scenario, it can induce a state of fatigue in the defense systems of cultivated animals due to the continuous stimulation of the immune system due to the microorganisms contained in the flakes, which may lead the animals to a condition of greater vulnerability. And although a scenario of co-infection with WSSV and Vibrio sp has not been evaluated, the possibility of its occurrence would result in the potentiation of the WSSV infection, especially in the system with BFT, considering the high vibrionaceaes concentrations accounted forAquaculture is currently one of the main means of obtaining food of aquatic origin in the world and its global production corresponds to 47% of the world production of aquatic organisms, equivalent to more than 80 million tons. Of the groups produced, the production of crustaceans stood out, which in 2016 was 7.9 million tons, with the marine shrimp, Litopenaeus vannamei, accounting for 65.3% of this total. However, this production has been constantly threatened by disease outbreaks, requiring a productive approach that applies biosecurity measures, adequate nutrition, promoting the immunity of cultivated animals and maintaining good water quality, to maintain homeostasis, which translates into if in the biofloc system (BFT). However, although L. vannamei kept in this system has achieved better zootechnical rates when compared to traditional systems, little is known about the influence of the transfer of animals to different cultivation systems, during the nursery phase, on zootechnical performance and immune resistance to White Spot Syndrome Virus WSSV. Therefore, the objective of the present study was to evaluate the influence of Litopenaeus vannamei exposure, during the nursery phase, and the alteration of the culture system, on zootechnical performance and immunological resistance to WSSV. Two systems were evaluated, Biofloc - BFT and Clear Water Recirculation - CW, in three steps: the first step, where the 10-day post-larvae (PL10s - 290PL/g), were maintained for a period of 10 days in the respective systems; second step, lasting 30 days, which consisted, at the end of the 1st stage, in the redistribution of the Pl20s for both systems, thus obtaining four treatments (BFT-BFT, BFT-CW, CW-BFT, and CW-CW) and the third step corresponding to the viral challenge. In these steps, it was determined: zootechnical performance variables; hematological variables (total and differential hemocyte counts); presumptive total count of Vibrio sp.; lesions suggestive of WSSV infection via histology and; infection and survival rate after viral challenge. The BFT system in terms of zootechnical performance, in general, proved to be efficient, especially in the early stages of the animal's life, with better results when compared to RAC. The results of the presumptive count of Vibrio sp. demonstrated growth in treatments originating from or maintained in BFT. Concerning the immune response and the influence of systems, hemato-immunological parameters were not influenced, however, it was observed that in a scenario of infection by WSSV, there was interference in the animal's immune response, resulting in a decrease in the amount of immunocompetent cells. Also, between treatments, there was a difference in the form of manifestation of the disease, as evidenced by histological analysis due to the higher concentration of suggestive lesions recorded in animals originating or maintained in BFT. However, despite the differences in the lesions found, all challenged animals were positive for WSSV via nested-PCR. Therefore, it was concluded that although BFT is considered a biosafety environment for cultivated animals, as it is a minimal or no water exchange system, in a WSSV infection scenario, it can induce a state of fatigue in the defense systems of cultivated animals due to the continuous stimulation of the immune system due to the microorganisms contained in the flakes, which may lead the animals to a condition of greater vulnerability. And although a scenario of co-infection with WSSV and Vibrio sp has not been evaluated, the possibility of its occurrence would result in the potentiation of the WSSV infection, especially in the system with BFT, considering the high vibrionaceaes concentrations accounted

Biblioteca responsável: BR68.1